Can't mount storage while flashing.

[Shaurya9008]

So I've been using a custom rom on my canvas nitro A311 for few months and today when I decided to change the rom in TWRP , The wipe was interrupted it deleted the previous rom and now I can't flash anything because it says 'cant mount storage' and my storage is shown 0 mb in TWRP. I can't use my phone because it don't have any rom and I can't flash one . Please help me.