With YOUR system it should be fine. The "300W" is only an estimate without knowing the rest of the system.
I would estimate roughly 200W for that system plus a GTX1050Ti under load with perhaps spikes above 250W so should be fine. That should be worst-case as a BASIC i5-3350P system uses about 88W under load. So add more RAM, 75W (ish) for graphics card and allow for spikes.
*See if there is a 6-pin connector on the GTX1050Ti card, and if so what ADAPTER the card comes with. You'd probably need a 2xMOLEX-> 6-pin adapter. (as I suspect you do not have a 6-pin graphics card power cable)