External hard drive not recognized after c drive clone

OK.  Here’s what I did.  My computer had a 30Gig hard drive (C:) which I wanted to change out to a larger one.  I also have a 500 gig drive (U:) connected via USB, which I use to back up my C drive as well as store photos/music.  Since my existing, my external and my new are all Western Digital, I downloaded the Acronis True Image software to use for the changeout. 
What I thought I could do is clone my C drive to my U drive, change out the C drive and then clone the information from my U drive to my new C drive.  I opened the software and pressed CLONE and told it to clone my existing C drive (internal 30 gig drive) to my U drive (external 500 gig drive).  A window opened which said it would change my drive to “BOOTABLE” and I clicked yes.  After a little bit, A window popped up which said my computer needed to reboot to complete the action, which it did.  I then took out my C drive, installed my NEW C drive,   My computer no longer recognizes my U drive.  If I go into control panel =>device manager it is listed,  but I cannot see it in explorer.  If I go to disk manager, I can see it and it says the disc is unallocated.  Is there anything I can do to try to retreive the information on the disc?

I think the problem was cloning and checking make drive bootable. The USB drive is not normally bootable. Cloning can be troublesome. I think you will have to put your old C drive back and see if it still works.  Then I would recommend making an Image instead of cloning. Macrium. EaseUS, and Paragon all have free programs besides the free Acronis on here at WD that should work. You will have tio make the Rescue CD to boot from that for these programs. You might do better posting in the internal drive section. This really doesn’t rrelate to the external drive.