I found a solution when using AI model for extracting information.
From AI model, 'predictionOutput' variable contains the "pageCount".
For example, my pdf file has 2 pages. So, 'predictionOutput' value likes this:
{"@odata.type":"#Microsoft.Dynamics.CRM.expando","pageCount":2,"layoutName",....}
My idea is to create a variable 'predOutput' and assign its values from AI model.
Then the number of page will be equal to:
split(split(variables('predOutput'),',"layoutName"')[0],'pageCount":')[1]
Best,