Apple Watch is not charging!

I have an Apple Watch Series 3 that I’ve had for maybe 5 years now. I can’t even remember the last time I used it, but I want to start wearing it again. I had the original Apple charger for it and then lost it so I bought a charger from walmart, and the watch will not charge. Everytime I turn it on, a screen pops up with a squiggle line and a green charger logo on the top. But that’s it.