Non Tilt Window Balance

I purchased 8 window balance -22" series 385 and they are the wrong ones. After looking closer I may need 390 series. I attached two photos of old and new one. You can tell the old one with he dirty string.

Can I return 6 old ones for credit. I don't want to wait so I'll order 8 if you can help me determine what I need.

On two of them I cut the ends off. that is why I only return 6. I put new new rods in the window but then couldn't get the window back in the frame. I really need some help. Two photos of the window are the top of the window. Now I can't get the old balance back in since the hook won't catch. I hope to hear from you soon Oh the side of the balance has p 2130.
Beverly Serene

I know how to install the window balance. I removed them from my windows and cleaned and sprayed with silicone the ones that were salvageable and reinstalled them. I need to purchase new ones and so my question is to look at the top and bottom of the two photos I sent last Sunday and help me figure out what to purchase? The ones I purchased from SWISCO do not fit my windows.
Your video was very helpful. I watched it a few times as it's been years and I sorta forgot how to do it. Thank you.

Thank you for the quick response. I placed a new order this morning. Wish me luck!