So I currently have a 9 pin switch, that looks like this:
And the project I'm doing calls for a 6 pin switch like this:
I'm kind of an electronics newbie and I was wondering if I could just use the 9 pin switch instead of the 6 pin. Would it be a massive problem and is not possible at all or could it work out?
All advice is appreciated, thanks for everything. :D
Here's the schematic: 
The DPDT switch is momentary, while the 3PDT switch appears to be alternate-action, so they're not compatible in terms of physical actuation.
From your schematic there's no electrical toggling going on, so you'll need an alternate-action switch, wired like this:
As a minimum you should beg or borrow some kind of continuity tester that can confirm which connectors on the switches are electrically connected in each (usually 2, sometimes 3) mechanical state. A continuity tester can be a VOM set to measure resistance, a battery and a light bulb, or a battery and a buzzer. You need to identify which pairs of connectors are "normally open" or "normally closed" since this characterises a switch's function. The other electrical characteristic of a switch is its maximum voltage and current ratings that should not be exceeded; you have to find where these are specified because you cannot measure them. It would be dangerous to use a switch intended for a low-current low voltage circuit in a mains voltage power circuit.
