Keep in mind, your dell is the desk top format, because you said the PSU is the 250W. And the case is small, you can only use the low profile GPU, and the TFX format PSU.
https://www.dell.com/en-us/shop/cty/pdp/spd/optiplex-7010
* if you had the mini tower one, you will not have problem for the regular GPU and the ATX PSU.
Now you need to read more about the PSU/GPU size, and make the measurement to make sure the PSU/GPU can fit into your case.
The most of gtx1050ti are the dual slot GPU, check its size ( W and L), also check your dell case space to see the gtx1050ti will fit into the case or not. Something like in the linker
View: https://i.imgur.com/WC8mooJ.jpg
And the PSU is something like:
SeaSonic SSP-300TBS 300W (Dimensions3.35" x 5.51" x 2.56" ) and 300W maybe OK, but you are better to get the 350W, because you need the headroom.
And you may or may not have the problem like this from nvidia tech support.
https://nvidia.custhelp.com/app/ans...t-graphics-card-into-a-certified-windows-8-pc
If you want to change the MB, recommend to forget about it, just upgrade the whole PC.