After I scan my files I get a list of what could not be scanned because it was password protected and when I try to scan them it says ‘error scanning files’. What do I do?
Welcome to the forum.
It’s a subject that’s been discussed many times and reveals many answers in the search function.
Here is the answer to your question. 
Short answer you don’t do anything, avast doesn’t know the password so can’t scan them.
Some examples of the file name/s and location/s would help to determine if the use is legitimate ?
Longer answer:
Many programs (usually security based ones) password protect their files for legitimate reasons such as AdAware and Spybot Search & Destroy, there are others (and avast doesn’t know the password or have any way of using it even if it did know it).
When you run scans with the above programs and you delete harmful entries that they detect, a copy is kept (in quarantine/restore/backup) in case you need to reverse what you did. These are usually password protected, you should do some housekeeping and delete old backup/recovery/quarantine entries (older than two weeks or so), this will reduce the numbers of files that can’t be scanned.
By examining 1) the reason given by avast! for not being able to scan the files, 2) the location of the files, you can get an idea of what program they relate to. You may need to expand the column headings to see all the text.
Files that can’t be scanned are just that, not an indication they are suspicious/infected, just unable to be scanned.
Thanks very much 
No problem, welcome to the forums.
Also … please come back soon, learn more, and maybe help others.