Combine Power Suplies?
Spec is 12W/M
You have: 4M x 3.

so, 12*4*3 Watt Power Supply Unit is what you need. 
Ie 144W.

This considering 100% usage, you should allow some leeway, 
so 150W one should be good.

Connection is in parallel.

So the PSU you need is like this: https://www.aliexpress.com/item/power-supply-48v-150w-48V-3-2A-power-suply-150w-mini-size-led-power-supply-unit/891473321.html

Also, if you found a higher wattage (200W or 300W) that is cheaper, then feel free to use that instead.