make sure its off when you convert to ship. dont turn it on until it is hooked to your ship. this thing has no thrusters or gyros so its gonna go crazy until you link it to your ship. so shut off the rotors. convert to ship. install in new ship, build gyros and thrusters. turn on rotors.

when i past this in i put some merge blocks on it so i could connected it ti a ship i was building but when i turn it into a ship to move it it starts to spin do u know why

I would recommend splitting this up so you have several versions of this.

Version 1 [small] Have only 4 small reactors.
Version 2 [medium] Have 8 small reactors.
Version 3 [large] Have 4 large reactors.
Version 4 [x-large] Have 4 large and 4 small reactors.
Version 5 [2x-large] Have 4 large reactors and 8 small reactors.
Version 6 [3x-large] This version (if possible swap the 12 small reactors for 4 large).