Well, figuring out what driver is pretty simple.
The solstrips are designed to use 24v @ 2.1A maximum. This gives you approx 50.4W per strip at full power. However, I can't recommend you running them at full power unless you have very good cooling.
For simplicity, let's assume full power is ~33w. Also, for everything below, let's assume you purchased the strips with their intended heatsinks.
33x3 is 100w (rounded up).
To run these three strips at full power (remember, implied 33w per strip full power), go with HLG-100H-24a, however, adding 3 more strips makes this driver not a good selection. You can either go with a larger driver, and just turn them down or up based on the number of strips you are running, or run two drivers (easier to wire an on off switch on the 120/220v side of things)
They also make other rated supplies.
AGAIN: SolStrips should not be ran at MAX without excellent cooling(active cooling strongly recommended)
HLG-150H-24A = 3 strips @ 50w each. 6 strips would be 25w each.
HLG-180H-24A = 3 strips @ 60w (EXCEEDING RATED MAX) however, 6 strips would run at a comfy 30w each, this is a very good efficiency and will run cool with minimal cooling. Passive air flow in the cab should keep strips ran @ 30w cool no problem.
How to decipher HLG's item numbers.
HLG - [Wattage]H - [Voltage][Type of dimmer]
So we know the Wattage number, 100, 150, 180 is pretty self explanatory.
The Voltage is self explanatory as well,
The type of dimmer is simple, but I don't use type B's as they require external 10v source/pots Type A has everything included into the driver and can be adjusted with a screwdriver.
In the end, I'd just get the HLG-180H-24a and run all 6 strips full time @ 30w per strip. You can always turn it down when you have clones. A kill-a-watt is handy for adjusting this.
Edit: Also, all these drivers I listed assume parallel wiring.