Can or can't

I have a 2012 Ford Fiesta 1.25. I want to convert the windows from manual to power. I have a complete set of doors, but they are 2014 models. Can I convert them?

Let's get this straight...

The 2012 - Manual crank windows or power?

2014 - Power or Manual Crank?

Converting crank to power - means a lot of work ahead of you - else the crank unit can be swapped over to make it manual to fit as manual, in a power window configuration. Power to manual is easier - you just don't connect power.

Oh boy! Not sure if I can help with this.

Black wires? Can you do a continuity check with the sockets and compare to your color coded ones to do up a map to "translate" the wiring from the doors you bought to fix the ones you have. Pin for Pin type of work, so you can map the piniout in comparison.

The hope here is; the connectors will match the wiring you have to connect the electric to the vehicle's electrical power, are the same in hookup so you don't need to make any changes - so all you have to do is connect and assemble.

But if not, you may need to change the black wires wiring in the harness to the socket of the door - to fit the harness of the vehicle you putting it into. That may require some tools to help separate the connector pin from the socket so you can re-wire the black wire socket to match your colored one.