The receiver you have is extremely old and obsolete. It is recommended that you upgrade your receiver and remotes. https://www.pssstore.net/products/liftmaster-850l-receiver-and-2-remote-package-1?_pos=1007&_sid=0b32c4273&_ss=r

I am unfamiliar with these model numbers. Are you able to send in a picture of the front and back of your current remote?