Advice on merging two blogs into one?

Hello, I have two blogs: My personal blog https://www.colinfitz.com – and then a blog for my Music https://www.colly.tv.

I rarely use the music blog any more I have not updated it in over a year, however I definitely want to keep it and all of its posts. However, I prefer the domain name of colly.tv – to the other .com one – and want to use this going forward as I want to start blogging more…

I was thinking of merging the two – backing up the colinfitz.com posts and importing them into the colly.tv – however – how can I make sure that I don’t lose my seo regards to the links etc that are out there for the .com site?

Any sugegstions? Thanks!