I have been transferring mac to mac using migration assistant over wifi for over 3 days

That's a long time. If your wireless environment is hopelessly crowded you might need to use a wired connection. You can connect the two Macs together directly with an appropriate cable, or through your router with an Ethernet cable. Either one of those two options may require that you purchase an adapter appropriate to the hardware ports they may have, but you need to tell us their exact model designations. There are at least a dozen different models.

Identify your MacBook model - Apple Support

Identify your MacBook Air model - Apple Support

"Older" can be as much as a decade and a half or more.