If the space traveler has enough scientific knowledge they will have a much easier time describing the location of the Sun to the aliens.
If they have a watch or other timepiece and it is working they can use it to show the aliens how long Earth time units are.
For example, the aliens could measure how long 10 Earth seconds are compared to their drens. But a more accurate ratio of seconds to drens would result from measuring 100 Earth seconds, or 1,000 Earth seconds, or 10,000, etc.
A second is now defined by a scientific fact:
The second [...] is defined by taking the fixed numerical value of the caesium frequency, ΔνCs, the unperturbed ground-state hyperfine transition frequency of the caesium 133 atom, to be 9192631770 when expressed in the unit Hz, which is equal to s−1.1
Scientifically advanced aliens should have their equivalent of the periodic table of the elements. So if the space traveler has a copy of our table of elements and can show cesium on it to the aliens, they will known which of their elements it is.
There are 60 seconds in a minute, 60 minutes in an hour, and 24 hours in a day, or 86,400 seconds in a day.
I once calculated the number of seconds in a year in my head while walking to school though I don't remember what answer I got. There are 31,536,000 seconds in a calendar year of 365 days, and 31,622,400 seconds in a leap year of 366 days, and 31,557,600 seconds in an average Julian calendar year of 365.25 days, and so on.
A light year is defined as the distance in a vacuum travelled by light during one Julian calendar year 365.000 Earth days long, or 31,536,000 seconds. So if the traveler knows that and can show the aliens the lengths of Earth time unit, he an call them how long a light year is.
The Sun is near the inner rim of the Orion Arm, within the Local Fluff of the Local Bubble, between the Radcliffe wave and Split linear structures (formerly Gould Belt). Based upon studies of stellar orbits around Sgr A* by Gillessen et al. (2016), the Sun lies at an estimated distance of 27.14 ± 0.46 kly (8.32 ± 0.14 kpc) from the Galactic Center. Boehle et al. (2016) found a smaller value of 25.64 ± 0.46 kly (7.86 ± 0.14 kpc), also using a star orbit analysis. The Sun is currently 5–30 parsecs (16–98 ly) above, or north of, the central plane of the Galactic disk. The distance between the local arm and the next arm out, the Perseus Arm, is about 2,000 parsecs (6,500 ly). The Sun, and thus the Solar System, is located in the Milky Way's galactic habitable zone.
So if the space traveler knows the latest (2023) estimates of the Sun's distance from the Galactic center, he can tell the aliens that the Sun is about 25,180 to 27,600 light years from the Galactic center. And the aliens can search their their data base for stars in that distance range.
And if the aliens know the distance of a light year, they know the duration of a year 365 Earth days.
And maybe the space traveler knowns the length of a sidereal year.
A sidereal year (/saɪˈdɪəri.əl/, US also /sɪ-/; from Latin sidus 'asterism, star'), also called a sidereal orbital period, is the time that Earth or another planetary body takes to orbit the Sun once with respect to the fixed stars.
It equals 365.256 363 004 ephemeris days for the J2000.0 epoch.1
So the aliens may also search their database for the length of Earth's orbital period.
And maybe the space traveler also knows about the Earth's orbit and has managed to teach the aliens the length of a kilometer or a mile in their units.
The semi-major axis of the orbit of Earth is 149,598,023 kilometers or 92,955,902 miles.
So the aliens may be able to search their database for planets with orbits with semi-major axis of that length in their units.
Maybe he can't teach the aliens the length of Earth kilometers and miles and thus the size of Earth's orbit.
But if he can teach the aliens the length of a light year, he might be able to remember that a light year is 63,241.077 Astronomical Units or AU, and thus that an AU is 1/63,241.077 or 0.000015812 light years. And an AU is the average distance of Earth from the Sun.
So possibly the aliens may be able to search their database for a star within the right distance range which has a planet orbiting with the right orbital period and also has the same planet orbiting at the right orbital distance.
That might narrow down the number of candidate stars significantly.
Here is a link to a similar question in the Worldbuilding Stack Exchange.
And my answer has links to other questions about finding the way back to Earth and their answers.
To be continued.