It depends if the name of the folder is literally "Misc" or if it just an unnamed folder which contains miscellaneous items.
If it is just a folder which contains miscellanea then you should describe it in words and write something like "Please look at the miscellaneous-items folder."
If it has a name you should refer to it using that specific name, set off somehow (like "quotes" or
codetext if your word processor allows for that): "Please look at the
Misc folder." Whether you use a period or not depends on the actual name of the folder.
Generally, you would not use the appreciated form of the word in a full sentence. You could use the abbreviation as a heading in a table, for example. In that context the period is truly optional in my opinion.
And as mdewey commented, you need a the before the noun.