There are some variations - but the basic connections to the motherboard are standard.
Dell is using standard PSUs these days. But you should list the model of your Dell for us just so we can check to make sure you don't have one of the older types that non-standard PSUs.
There is a really good deal going on now with the Antec NEO ECO 400C 400W
$45 before a $10 rebate. And a $5 off promo code till Sept 8th. Also free shipping.
That could take your final cost down to $30 for a strong 400W CPU with 30Amps of +12V power that would support a really nice gaming video card upgrade.