Extract IMEI from Nexus 5 TWRP Backup files

i hope you guys can help me out here. Today my Nexus 5 has been stolen. Now i want to prosecute but i need my IMEI. I am currently not at home but i got my laptop with a backup made by TWRP.
The folder looks like this:

http ://puu.sh/ nzexP/cfbff68baf.png (remove the spaces, i am new here thats why i cant post links yet)

As you can see there are some files and also two files efs1 efs2. But i dont know how to extract those or where to find my IMEI in that files.

Could someone please help me with that?

Thanks in advance