Can someone explain to me what size rear rim I would need if buying from say eBay?

[.:SAmSuNG:.]

So we have this old womans town bike from the early 90s that needed some TLC.

So i ordered some new inner tubes and tyres (700x35c) which fit fine but I thought I would give the spokes a tighten but ive managed to buckle the wheel some and tbh I don't think I have the skill to get it back straight.

The gears are a 7 speed shimano grip shift on the rear but im unsure what rim I will need to use the tyre and the brakes line up etc. I would probably just buy a rim with the rear cassette if that would work and be easier.

Would something like this work?

26 " ALLOY REAR MOUNTAIN BIKE WHEEL & 7 SPEED SHIMANO FREEWHEEL

I have measured the rim and it seems like its 25" but im not sure where i should take the measurement from.

Thanks.

 

[.:SAmSuNG:.]

I found this if it helps.

Does it matter about the gears as long as I get the same amount?