External hard drive files missing

I have a Maxtor One external harddrive on which i store my graphic images. Recently i had replaced my hdd to a larger size and i' would like to make the old hard drive as an external hard drive. I copied the old drive onto the new one and installed the new one. Now when i try to open up my new hard drive it shows an error message stating that your external hard drive files seems to be missing on your system. Can any body tell me that what i need to in order to get rid of the above issue? Kindly provide me the correct solution for the above issue.

Had you tried out to use explorer in order to find the missing files on your system? It might be that your drive has filesystem may have damage on your pc, even your Disk Utility--> First Aid can't recognize because of the simplicity of that program.

File-systems do get damaged randomly for no discernible reason, but that is usually quite rare. Ensure that your External Drive is disconnected from your computer during the installation of your Operating System as this will eliminate the problem altogether.

According to me you should try to use a third party, data recovery software to access the data on your system. Try to run some recovery software just to make sure that your system may been not affected from virus. You can also try out Recuva program on your pc. As it is also known as pronounced "recover" and is a freeware Windows utility to restore files that have been accidentally deleted from your computer. It will even bring back files that have been deleted by bugs, crashes and viruses on your system. Another way you can try out is by booting your pc into safe mode to access the simple file sharing option.