Pictures will help. If your setup is like mine I would remove the A/C filter and locate the junction box. Remove the jb cover and snap a pic.
If you have a wall thermostat carefully remove whatever cover or screws it takes to expose those wires and snap another pic.
If you plan to power the A/C with an extension cord then all you will need is a Male adapter from home depot with 3 wires coming off the back. Attach those to the A/C junction box where you removed the existing wires, which might be yellow romex.
Make sure to check voltage if using a long extension cord. Of course use the thickest and shortest cord possible. If you get the A/C running probe the voltage where you connected your adapter to the A/C jb. I think most guys say if its below 110v you should buy a thicker and/or shorter extension cord.
Use a battery and some wire to temporarily power your thermostat.