Are you close enough to an REI dealer to let their shop handle the chain installation? Might be easier and cheaper in the long run. Especially if you don't have the original chain to use as a guide for the replacement.

When I replaced the chain on my long wheelbase comfort hybrid I just counted the links on the original. Two or three times to be sure. It was so worn and elongated I couldn't just lay the old and new chains side by side for comparison.

I bought the replacement chain at REI and told the mechanic I needed a 122 link chain. KMC chains come in boxes of 116 links. He just gave me a couple of lengths of new 6-link chains cut from new chains installed on other bikes. I spliced 'em, put on the correct Missing Link, no problems with fit.

It skips a bit in gears 5-7, but that's because the original Shimano MegaRange freewheel is worn out too. I'll replace it soon. Didn't realize how much I'd ridden this bike, especially on gravel and gritty rural chip seal, so the moving bits wear more quickly.

Well, the problem is, the chain came stock with 118 links, and felt a bit too long. And since the gearing was too high, I then changed the crankset to gear it down some. I dropped the chain down to 116L for the change, and that seemed ok. But the gearing still want' low enough for me, so I changed out the rear cassette for a lower geared one. That gearing feels about right, but the chain was then too short, so I went up to 118L. That gearing feels good to me, but as I reported earlier, the chain still felt too short. I just now in the past hour have added two more links, bringing the chain up to 120L as I said I would try. Turning it on the stand felt better. I'm going out on a little test ride right now to confirm. I'll report back in a bit, so stay tuned! lol

Perfection! Finally! Yes indeed, 120 links is the magic number, and this bike is running and shifting the best it has since I bought it!