Media Density Issue

Hi, I'm looking after my businesses backup and recovery solutions while a colleague is on holiday, I have a bit of experience, but it's fairly limited. My colleague left me a box of new tapes, barcodes follow on from the ones I'm using as data stores, but when I've added them into the library and updated the inventory the Media Type is showing as 8mm, where as everything else is HCART. The tapes are therefore not being used, and I really need to get them working so I don't have to expire a load of data early. Anyone know how I can change this? Or delete and re-add with the correct media type? The library is a Quantum Scalar i500, the tapes are all LT04, and the Netbackup version is 7.1.0.3

Any help would be appreciated, even pointing me to some documentation, as I've not found anything yet that helps me with this.

Many Thanks,

Katie