How do I convert incorrect characters an Excel file back to normal?

I cannot find a solution to this problem. I have thousands of rows of data and all the French and German accents are messed up in those words, example:

ÌɉۼÌã‰ÛÁ

Is there a way to change this back to another format, or is it too late? I cannot change the data source by the way, that isn't an option. I'm stuck with this sheet. If I cannot change them back, can I highlight them in some way?