How to erase encrypted partition hidden on USB but I lost the USB

So please bare with me as I’m a total amateur but this is what’s happening :
Years ago when I got paranoid about the internet I stupidly got in over my head when I decided to encrypt the majority of my computers memory using truecrypt. I had read somewhere that to make it impossible to access it’d be smart to only make it mountable from a file on a USB . I did this and then…. Somehow lost the USB. So basically most of my computer’s Memory is now inaccessible because I can’t access the file that I used to click in on order to mount the voluMe. PLEASE forgive Me I don’t even know if I’m using the right words, I’m just hoping someone can decipher my post and help a girl out! Thank you so so much in advance. Ps Kali is currently installed on it but it’s an HP from 2012 I can figure out model number if that is relevant. I’m aware someone like me should not be messing with anything this Hectic so please do not insult me…I get it Ok. 🙁