|"Didn't get another plug"|
Hopefully you re-check your post.
Of course you didn't "get one". You should already have one (or more) available. You should NOT need to buy anything. All you need to do is take one of the unused plugs from the power supply & connect it to the card. There's *usually* a couple of extra/unused plugs tucked away *somewhere*. Trace the wiring harness from the power supply & see if you can find one.