Welcome,
Did the game work before since you've had it or did you get it like this?
That pattern of junk on the screen happens briefly when all DK PCBs are powered up, but the CPU clears the screen once it starts running program code.
If it stays on the screen, it means the Z80 CPU is not running. The CPU socket could simply be dirty, or the CPU could be bad or missing altogether. If the game ROMs are bad, missing or not properly seated in their sockets it will also do this because then the CPU has no code to run. It could be a bunch of other stuff also, but those two are usually the first suspects.
Lastly, that screen of junk is supposed to have a black background with characters and graphics of various colors over that. Your image looks like maybe you have a non-Nintendo-compatible monitor in your cab. DK PCBs output inverted video and if you have a standard arcade monitor you need to have a video inverter in between them.
