how do i migrate everything (incuding os) from mac to mac without firewire?

Either get a TB to Firewire adapter and maybe cable or get a TB to Ethernet adapter and use a Gigabit Ethernet cable to migrate.
Or remove the HDD from the old MBP and put it in a USB 3.0 enclosure for 2.5" S-ATA HDDs, they should cost around 20 €.

 

I used an Ethernet cable (assuming both Macs have one. The advantage to this is you probably already have one. Just leave it transferring overnight rather than sit and watch the progress bar.

 

I migrated from iMac to iMac using an Ethernet cable.

I dont think migrating the OS is likely to work though or even if it did, is advisable. I would install OSX afresh on the "new old" macbook, and use Migration Assistant via machine to machine or Time Machine disk, to migrate data and apps across.

 

Probably easiest and fastest to use Migration Assistant or Time Machine to put your data on a USB hard drive.