Welcome to the forum
Which Arduino board are you using and which board is selected in the IDE ?
Please post the sketch that you are trying to compile, using code tags when you do
This is the easiest way to tidy up the code and add the code tags
Start by tidying up your code by using Tools/Auto Format in the IDE to make it easier to read. Then use Edit/Copy for Forum and paste what was copied in a new reply. Code tags will have been added to the code to make it easy to read in the forum thus making it easier to provide help.