Could you take a picture of the speakers or at least count them and relatively describe their location?

It should be something like "3 on the wall where the tv is, 2 behind me" but if there are 7 there should be an additional set somewhere. It probably isn't more than that, but if it is, describe it a bit better. There are a lot of ways it could have been done before, there may or may not be an in-ceiling woofer (is one speaker way bigger?)

I/we need to know this to really recommend a receiver.

The receiver will need to be near those wires, have input from all the sources, and then have hdmi over to the tv (in some cases, this is far is the only reason I point it out, and you would be surprised the number of people that didn't really consider that).

Since your wires are unlabeled and multicolored, which colors are they? Red and black? Or are their 4 colors? Or are they some other color but one has a white stripe down it?
You are going to have to figure out how the wires are paired- 2 go to each speaker. If you notice it's "sets of pairs" of wires, it's easier- those will be your left/right pair of the same speaker. If you are nervous, grab a ladder and pull one of the speakers down to see which colors are wired to it, but usually it's going to be RB to one, WG to the other. White and red are usually positive, green and black negative. I'll stop the explanation there unless you have something else or still don't understand

You SHOULD label your wires somehow as you do this next step.
I would banana plug all the wires, because you're going to be connecting them a lot. I like Sewell Deadbolt banana plugs.
What you will have to do is plug each paired set of wires into the center channel , figure out which speaker plays, labeling the wires, and then plugging them into their appropriate receptacle once you know where they are (I would wait and put them all in instead of adding channels one at a time).
I would turn the receiver off between each connection.
If there's 2 or 3 pairs and one unpaired wire, it's your center probably
Let me know what you need help with.