Unable to download Microsoft teams

Have you looked to see if your device is on the list of compatible devices ?

https://apps.apple.com/us/app/microsoft-teams/

I’d post it but it’s too long.

Are you really running iOS 10 as shown in your equipment line? According the the Microsoft information here;

https://docs.microsoft.com/en-us/microsoftteams/hardware-requirements-for-the-teams-app

According to that, Teams only supports the last two iOS versions, so that is iOs 12 and 13.\:

The listing Skydiver 119 posted show the oldest iPad that Teams will work on is the original MacBook Air. It can run up to iOS 12.4.X.

Microsoft only supports their MS Office mobile apps for iOS 12 or 13. They only support the current and next most recent versions of iOS or iPadOS. That is Microsoft’s policy so Apple cannot help you with that.