I have had to change my pc & used easeusto do transfer tool but when I try to open a document in LibreOffice it says that it does not exist

I can see all my documents but none will open for me to print or change anything.

If you expect any decent answer, read these guidelines and edit your question to make it understandable by anyone not looking at your screen.

Mention your OS name and LO version. Are you trying to open your documents from the “recent doc list”? If so, have you transferred your files following the exact same architecture of directories (folders) with same names and positions?

Do you click on a desktop shortcut? This shortcut is associated with a specific path. If you reloaded your PC with a different architecture of directories, the shortcut has become invalid.

Warning! On this site, answers are reserved for solutions. So edit your question to provide additional information.

but when I try to open a document in LibreOffice

You click on the thumbnails in LibreOffice Start Center? If yes - use File -> Open and navigate to the directory where they are stored and select the file using the file picker.

Please see my answer to question 267726 . Cheers, Al