Stellarium is a free planetarium software, and it allows you view the position of stars in the sky at any date.
Sirius and the Pleiades are actually rather close in the sky. On the line of Orion's belt, on opposite sides. So for much of the the winter months, both are visible in the sky. For example in mid-December, they will be visible at midnight, in south-western skies. At the time of writing (8th October) they will be visible in the early morning.
It is a well known starscape, with Orion central, the Pleiades and the V of the Hyades on one side, and Sirus, scorching on the other.
Of course, the Pleiades and Sirius are "fixed stars", so the separation between them doesn't change. There is no time when they approach each other.