micky wrote:

I have a bunch of power supplies that I took from full-size PC's but
this PC is one size smaller, 12"x 12 or 13 x 3.5. So they probably
wont' fit, right?

Be careful, some Dells use non-standard wiring of the PSU connector.

If you compare the colours pin for pin, you could test using one of your
spares, even if it meant leaving it outside the case.