It should but I can't give you a definitive answer based on the information provided. For that you would need to open the specification sheet found under the header "Info and Guides" on the Home Depot product listing page, and using a tape measure compare it dimensionally to current installation.
Yes Slant Fin 30 baseboard can be cut and typically is cut during the installation process. However cutting it is not easy and takes some experience. When I was an apprentice plumber we used tin snips which was both difficult and left a nasty edge. In more recent years I have begun using a chop saw. I use a blade for metal and I make sure to secure the product while cutting. I also make sure to ware eye and hand protections. Now I notice you are looking at enclosure only as apposed to complete baseboard with the element. Therefore you should keep in mind the purpose of enclosure only is to act as a pipe chase in an installation. It is not intended to re-wrap existing element where the existing enclosure has become aged. People attempt all the time. However depending on how the existing baseboard was installed it can often be impossible to replace the enclosure without removing the element.
I believe that Home Depot does carry the 8’ length. While I think the Slant/Fin does make “kits” that comes with the end caps, what I purchased from Home Depot was a 6’ length and a separate left and right 4” cap. Good luck, John