how do I upgrade from GB 5.1 to a newer version with 10.8.2 ?

I am currently running Mac OS 10.8.2, yet only have Garageband 5.1 (aka Garageband '09).

I cannot find anywhere how to upgrade to a newer version of Garageband.

I see the newest (?) seems to be Garageband 6.0.5, but when I tried to download it, it tells me "GarageBand 6.0 or later is required to install this update." and will not allow the update to continue.

I cannot find a download for version 6.0 on the apple support page. And even then, I don't know if it will tell me that I need to install an earlier version, before I attempt to update to version 6.0..... etc.

I hope my question makes sense?

I appreciate any and all responses, and appreciate your time. Thank you in advance.

Ultimately, I am trying to use my Behringer Xenyx X1204USB mixer as an interface for Garageband.... if that's even possible?

Again, thank you for any help with this. I really appreciate it.

You can reach me at: mr.gixo@gmail.com mr.gixo at gmail dot com

Thanks.

-Brian