How can I move email messages from external pop3 account's inbox into my zoho mail inbox.

How can I move email messages from external pop3 account's inbox into my zoho mail inbox.

I have connected my zoho account with an external pop3 acoount that I have.
My intention was to receive all messages into the same inbox,
After setting everything up, I realized that a separate inbox is created for the pop3 account.

My final decision was to set permanent forwarding of messages form my other (pop3 account) to my zoho mail address.

However, numerous messages have already been downloaded into the separate pop3 inbox. Unfortunately, during the pop3 account setup, I had chosen not to keep original messages on the server of the pop3 account.

I am trying to find some method of moving all the pop3 account's messages into my zoho inbox (and then remove the pop3 account).

Please help me.