I want to publish a model on Asset Store, but i don't know how to create textures in ".tga" file.

I tried it in photoshop but Unity team does not accept my model for publishing. Please anyone guide me, how can i create textures that unity team accept my model. Thanks in advance…

Targa TGA is a very common image format - I’d be very surprised if Photoshop doesn’t support it (I use GIMP, which certainly does). Just File → Save As.