Okay I tried to do search for position but the first thread did not help.
Then I clicked the green button on the left "B4A Library" and the first thread was now RandomAccessFile.
I did not check if position is part of RandomAccessFile but I guess it is.
Also be aware that if copying only snippets from the forum then sometimes essential bits can be missing. In your sample is it possible that Position was maybe a Type declared is Process Globals for example?
Open the .b4a project file in a text editor.
You'll find it contains a list of the required libraries - and one of those libraries will contain the Position object.