@Theowl22
Should just be able to attach the HDMI cable of your Express 4k to the new TV and be good to go. If your new TV is different manufacturer from your old one, may have to reprogram the Roku remote for your TV functions (power and volume).
Settings/Remotes & Devices/Setup Remote for TV Control
Roku Community Streaming Expert
Just another Roku user... I am not a Roku employee.
Insignia RokuTV, Ultra 4660, Premiere+ 3921, Express 4k+ 3941, Streambar 9102