Hey clemens48,
With POP accounts, normally the emails are downloaded to your device and deleted from your email service providers servers, unless you're provided an option to keep them on the server. Have you checked with your email service providers webmail site to see if the emails still appear there too? If they do, you can simply add the account to your new iPad and the emails should sync over. Here's how: Add an email account to your iPhone, iPad, or iPod touch - Apple Support
How to set up your email account automatically
If you use an email provider like iCloud, Google, or Yahoo, Mail can automatically set up your email account with just your email address and password. Here's how:
1. Go to Settings > Mail, then tap Accounts.

2. Tap Add Account, then select your email provider.
3. Enter your email address and password.
4. If you see Next, tap Next and wait for Mail to verify your account.
5. If you see Save, tap Save.
If you don't see your email provider, tap Other to add your account manually.
Keep us posted.
Take care!