Best solution for storage?

Hello, I hope this is the correct place to post this but I'm seeking some help with a long term storage solution.

To clarify I currently run a Jellyfin server from a Lenovo ThinkCentre used exclusively for that purpose with a connected 6TB Seagate Expansion drive, now whilst the 6TB is well within a sustainable state currently, I've burnt through 2TB of the storage on there so far.

My question is, how can I future proof this, I considered getting something to ecaptulate the drives to power them all in a space efficient way so I can keep it close to my ThinkCentre but I'm not too sure if this is the best way to do things, I guess my main question is, should I need to, what is the best way to expand my storage? I have multiple external HDDs ranging from 2TB up to about 5TB but the problem would be powering them all and having the space to insert them into the ThinkCentre.

Any help is greatly appreciated and apologies if it's a super noob question lol.