Can’t download Instagram from App Store

Hello 132stop,

It sounds like this previous Apple ID was used to originally set up the iPad mini. Which is why it's asking you to verify the download using that password. In order to solve this, you'll want to check the following to determine if the iPad is still linked to your Father's Apple ID:

1. Go to the Settings app
2. Tap on [Name]
3. Tap on Media & Purchases
4. Verify the account signed in here.

If your account is signed in here, then you should be good to download new apps under your Apple ID.

If his account is here instead, then you'd need to proceed to these steps:

1. Go to the Settings app
2. Tap on [Name]
3. Tap on iCloud
4. Is this your iCloud account sign in or your Father's iCloud account?
5. Check in the Find My section, is it enabled?

If your Father is signed in to the iCloud account with Find My enabled, then he would be required to remove the iPad mini from his account in order for you to restore it to factory settings and set it up (to associate it with your iCloud account and Apple ID): Restore your iPhone, iPad, or iPod to factory settings - Apple Support

In this case, you can share the following with your Father to accomplish this: What to do before you sell, give away, or trade in your iPhone or iPad - Apple Support

Let us know if this helps out, take care.