well i'm quite the beginner

i have a blues backing tracks cd and i want to learn and run on scales
what does it means blues in E2 ?
E2? Not a clue.

Maybe it's in the key of E and it is track 2?

Play an E minor pentatonic over it and see if it sounds good.
Blues generally means a I IV V progression in whatever key. E2 generally stands for an Esus2, or an E major chord with a M2 (F#) instead of a M3 (G#). I would assume it means Blues in E, which would be E, A, B. Scales you could play easily over it are E minor pentatonic or E major pentatonic, to name a couple.
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It could mean 2nd position Blues scale in E. The first position is usually the pattern at the open or 12th fret, with the root on the 6th string, based around the "E" shapes using the CAGED system.

The second shape position would be around the "D" shape using the CAGED system. The root would be the "E" at the 4th string 2nd fret.

Does that make sense in the context of your jam track?