Even if Galaxy can auto-detect the format properly (.fastq is let's say quite generic because would mean only sequences with scores) there are differences in quality score systems which in turns they could affects the format of the files.
Accordingly, it is always good to know to which quality score system your data belong.
i.e. if they come from the ILLUMINA platform they quality score system is Sanger (from 2011) and you should choose manually .fastqsanger (using "edit attributes", little pen on the icon from your loaded data). You can do it directly before importing them into your history or once loaded). It's just a matter of formality.
I suggest to you to read carefully some information, you can start from these very helpful links: