Nominal voltage, as explained above, is 3.7v. Most in the bike industry have settled into the standard for 48v being 13, 3.7v cells in series. This charges to 54.6v.
Others prefer a bit more speed, a tad more wattage, and run 14s. This charges to about 58.8v,, or some will undercharge a 14s, and go to somewhere around 57-58v.
Most 48v controllers have an absolute max rating of the capacitors inside of 63v. Open your controller, see 63v on the little cans inside,, there you are,, your max is 63v. Of course,, some push that some,, after all, your battery will sag a few volts as soon as you apply throttle. So with some risk, folks are known to run 15s,, or even 16s, especially if they also undercharge a tad.
And by the way,, if you are looking at power tool batteries, like mowers and trimmers, ,, they tend to go by 4.2v,, and call a battery 50v,, instead of 44v.
As for your motor itself,, its a 28 mm wide magnet direct drive. I've briefly run those at 4000w,, 40amps controller and 96v nominal. At 3000w,, usually a 72v 40 amps controller, you can run out about 10 ah worth of battery before the motor starts to damage itself. About an 8-10 mile ride full speed of 40mph.
A better, longer lasting plan for those motors is not to try to get 45 mph out of them. Let your full speed be around 30 mph or so, and run 48v 40 amps controllers. At 2000w it will ride very perky, and only risk overheat if you seriously overload one and ride up hills.
If you want 3000 or more, then you really must go to a much wider motor, with a lot more copper and wider magnets. then go for 5000w.
Now,, as for your battery plan,, bleah,, those holders I mean.
Assuming your current controller is 22 or 25 amps,, you need enough cells in parallel to put out 25 amps continuously.
A good rule of thumb for that is take the cells max amps rating, and cut it in half. So say one cell says it can do 4 amps,, calculate at 2 amps,, 25 amps will require about 13 cells in parallel. But you wont pull 25 amps continuous with that controller,, so figure on about 18 amps to cruise full speed, at 25 mph or so. For this example,, 18 divided by 2 amps,, you need 9 cells in parallel. Your cells might be better, or worse,, but at least 100 cells sounds about right.
That's the minimum,, if the cells are not real great,, 20 ah is a bare minimum. 30 would be my suggestion, unless they are top of the line cells.