To check if an excel file is already created in the sharepoint, I have to add 3 steps. After clicking on the “+”, in the “search” field, put “initialize” to select this option:

Fill the fields and in the “value” one, let it blank:

NOTE: in the “name” field, put whatever you want

Click on the “+” and in the “search” field, put “sharepoint get file” to select this option:

In the “advanced parameters”, click on the “down arrow” to select “filter query”:

And put:

• Option 1: FileLeafRef eq 'XXX.xlsx'
  
• Option 2: FileRef eq 'https://sharepoint.com/YYY/XXX.xlsx'
  

NOTE:

• Option 1 will look in all folders and subfolders inside the “root folder” (in my example, it is “(shared) documents” library), replace “XXX” by the name of your file
• Option 2 will look inside a specific folder located in the “root folder” (in my example, it is “(shared) documents” library), replace the link path by yours (YYY is your folder and XXX by the name of your file

Click on the “+” and in the “search” field, put “condition” to select this option:

Click on the first “choose a value” field then click on the “lightning” icon to select:

Click on the second one then click on the “lightning” icon to select:

NOTE: it is the name I put for my “initialize” step

Now, in “true”, I put the “send an email” step but you can put whatever you want, so if the file doesn’t exist, it will send me an email, if not, it will do nothing.