Volume controls for Garageband

I have an iPad Pro 9.7 with iOS 11.2.6. I have down loaded Garageband. When I open it to start recording there is no way to adjust the input volume level when trying to use a microphone. The input volume bar does not show the slide button. When I use the built-in mic the volume is too low. I also have an iRig Cast mic and when I use it the volume is way too high. Still there is no volume slide button. I have just recently upgrade the iOS to 11.2.6. I had successfully used the iRig a month or so ago before the 11.2.6 upgrade. Hope someone can help.

Thanks,

Jim