Validate from Fabric whether the file exists

[wsepulvedaCol]

I'm working on Fabric, and I need to load data from an on-premise folder (A) to another on-premise folder (B) or alternatively to a lakehouse (C). The loading process depends on whether the file (X) has been created or not in the original on-premise folder (A). How can I validate from Fabric whether the file (X) exists or not before triggering the loading execution?