Replace Project Bitmaps

Hello,

I'm almost finishing my game and, silly me, I've used all my bitmaps in single files, now I want to pack them in sprite sheets (using Texture Packer)

My question: Is there any easy way to replace all the bitmaps I've used in my scenes and prefabs by the same bitmaps (same file name) but packed in my sprite sheet? Or I've to do it one by one by hand?

If someone has a solution for this one it will save me hours of work and I will be forever in debt

Thank you.