While your question is simple Chris, the answer can be a bit complicated. I would say to you, don't approach this as a guitar player or a bass player, but as a MUSICIAN. Practicing scales and chords are great for technique. I practice them every day. At Mushroo said, learning songs is where it's at... but you have to approach that the right way too. You have to remember that when you are in a band, the band is ONE UNIT of several musicians. You have to learn to understand your role. And that while you may feel that you've been "displaced" from guitar, they actually displaced you to a role where you have to lead... while you're following. You and the drummer are laying down the framework for everyone else to play inside of. You set the groove. You set the mood. So, yes learn your scales, chords and songs... but learn how the bass sets the character for the tune and everyone else. And at the same time, you have to also get "big ears" so you can play off of everyone else as well. As I said, you have to become bigger than just being a bass player.
Having said that, one thing that can help (IMO) is, in the process of learning the songs learn the music. The best investment I've ever made is buying the app "Guitar Pro". That will give you access to thousands of free music (files). And what's cool about the Guitar Pro is that you can see all the parts for the band, separately and often as a score. While others have mentioned scales and chords and learning music... nobody asked you if you could read music. While many *get by* without knowing how to read music, imagine how much more versatile, and probably more in demand if these guys could read music. And if you're not a good improviser (like me) being able to read a chart can let you fake your way through, as long as your interpretation can be musical and creative.
And as part of the above, have you taken the time to understand root progressions and how they are the building blocks of music theory? IMO that is essential to begin to understand bass playing. It will help you with your improvisation, as will chords and scales, especially with old school stuff. The good news is that the essentials come quickly and are pretty easy, especially coming from guitar. The other good news (or bad news if you want to take it that way) is that becoming a well-rounded musician is a life-long process.
Good luck.