Chicago,
First go to Settings > General > and look under "USE SIDE SWITCH TO:" If it is set to Mute, then check your side switch to make sure it did not get muted accidentally (you should not see the red dot). If it is set to Lock Rotation then bring the Control Center up by swiping up from the bottom of the home screen and make sure Mute is not ON.
Use Control Center on your iPhone, iPad, and iPod touch - Apple Support
If this does not work for you, try a forced restart. Hold down the Home and Wake/Sleep buttons at the same time for about 15-20 seconds until the Apple logo appears. Ignore the "Slide to power off" text if it comes up. You will not lose anything.
Post back if none of this works as there are other steps that can be taken but these are the most common and easiest.