Dual Motor LiftBoard Battery Upgrade

Hello all! I have finally got into the electric skateboard market after many years of envy by buying a very cheap dual motor liftboard off Facebook Marketplace earlier this week and love it. I know it’s “garbage” but i dont really have a budget and i got it so cheap it fit right in the budget. I like the torque and top speed fine but find i want to improve the range. It currently has a 6S4P pack made with Lg2200mah 18650 batteries

running 2 900W brushless motors. I get 8 miles of range with moderate riding and a 16mph top speed at 180pounds and it takes 4 1/2 hours to charge from dead to full. Im wondering if it would be “plug and play” if i bought the same used but good batteries from this company that pulls them out of internet modems

(because i can get 40 for 20bucks and remember i have no budget) and get a new longer nickle strip if i could use the same wiring and everything from the old battery and make a 6S6P one with those. Also would i need to change anything besides the length of nickel strip on the pack so more batteries can be added and expanding the housing its all kept in? To my understanding i shouldent right? Because, everything is the same except the “pool” of power the motors are drawing from is just bigger since im just added more batteries in parallel. I’ve only looked into this for a day and Im a complete noob to this whole thing so if anyone out there would kindly point me in the right direction that would be awesome. Thanks so much