HELP: I can't turn the white transparent in my AI generated image

So I used the AI generate function to make my images - i've then used the effect>sketch>graphic pen option. I need all the white parts to be transparent since they'll be overtop of a coloured background - but i cannot for the life of me figure out how.

Here's what i've tried so far:

- I'm unable to use the object>expand/ window>image trace function on the image (I think because its an AI image? im not sure).

- I've tried exporting it as a png and then reimported to fix this issue but still not allowed to (plus the quality turned terrible but that could be my fault for sure loll). 

- I'm unable to recolour the image and switch the white to transparent (#ffffff00) - but maybe theres another way that im unaware of or i'm doing that wrong?

I'd love any tips because i want to keep all the black dots while deleting all white parts - here's a picture of what we're working with and the background i'll be using