Can I reinstall Mac on a MacBook from an iMac using a cord

You could create a bootable key on the iMac to be used to reinstall macOS on the MacBook Pro: Create a bootable installer for macOS - Apple Support. I'm unsure about a solution using a cable between the 2 Macs.

Good advice so far, & yes a cable might work, depends which ports these 2 macs have, which exact models are they?

If they have the correct ports then you'd put the MBA in Target Disk Mode...

Transfer files between two Mac computers using target disk mode - Apple Support

Be sure NOT to use a USB flash drive that contains files you need. Part of the article that 6x6 links is: