Welcome, @Raul_Carlos_Mainar_J
The qiime tools are expecting the fastq sequences to have a specific format in the @ sequence identifier line. The tool is reporting your sequence identifier as something different.
If you are not sure what “Casava” format means or looks like, this guide can help → FASTQ format - Wikipedia
There isn’t an automatic way to change the sequence strings but the sequencer would have output that format originally if you can still get access to that data.
Or, you can try using Manipulate FASTQ reads on various attributes. Scroll to the bottom of the form to see example usage plus a tutorial.
Hope this helps! 