If you want to record your iPad screen and save the recording without an error, you need to turn off the microphone recording. However, if you want to record the screen with audio (system and microphone sound) on an iPad, you need to try some third-party screen recorders.
Here's a list of third-party iPad screen recording apps to record the screen with audio:
Record it!: Screen Recorder
DU Recorder
TechSmith Capture
Screen Recorder +
Live Stream Apps & Games
Web Recorder