Hello and Welcome. Way too small an enclosure to get any type of heating temps correct. Also, you will need room for water dish, food dish, hide and room to walk, so, no small enclosures like the ten gallon.
Tube type, size, and distance from the tortoise are all important factors. The simple, not so inexpensive way to answer is to measure the output at the height that the tortoise is exposed with one of the UV meters. There are several discussions here and elsewhere on the internet about which one to choose and how to use them.
I agree with the other thread contributors, a larger enclosure will be needed sooner or later, so just go there sooner. There is also the idea of a few hours of sun each week making inside UV light not necessary at all. This can be a much larger enclosure and may be better depending on where you live (climate) and how secure (other pets, predators, people) an outside area you have to work with.