Calculated column with check if column value contains a string

AndreaPJ Are you getting the syntax error while using first formula you shared in your question? Or it is not returning correct results as expected.

Note:

1. Sometimes comma( , ) does not work in formula (it is based on language or regional settings on your site). So in that case use semicolon( ; ) instead of comma( , ).
2. Use correct display name of your SharePoint columns in above formula.
3. Wrap column names inside [] if your column name has space in it. For example: [My Column Name].

If it is an issue due to comma, try using formula like: 

=IF(ISERROR(FIND("CD";[Format]));"XX";"CD")

OR try using this once (with comma and with semicolon): 

=IF(ISNUMBER(FIND("CD",[Format])),"CD","XX")

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