The roof mount positions are the same on the T6 and T6.1 (and I think the T5/5.1) so if you have the factory black bolt/washer assembly in the roof gutter you have standard mounts.
Some higher end variants come with "roof preparation" which is a rail foot system that needs a different solution, so if you have a silver rail filling the roof gutters it's probably that.
My MY21 Caravelle 6.1 had standard roof mounts.
The Rhino Bars seem to come with a foot that can either bolt direct or use the rail prep, assuming you are a SWB being a Caravelle this is the four bar set, have a look at the fitting instructions:
4 x Rhino KammBar Pro Aluminium Roof Bars - Volkswagen T5 Transporter SWB Tailgate - Rhino KammBars are the most aerodynamic roof bars in the Rhino range.
www.rhinoroofracks.com