Copy & paste is awfully broken in Prime in various aspects.
So I guess the simple way you tried was thus successfully blocked by PTC
So you simply may create a new table via copy & paste and delete the old one. Not satisfactory, I know.
A table actually is a collection of a couple of independent nx1 vectors. So what you created are three 3x1 vectors with three different variable names.
Are you sure that this is the suitable data structure you need for your further calculations?
You may use the function READEXCEL to read in the data from the external Excel sheet. Either three times to create the very three vectors you cretaed via the table or in one go by reading in the data in a matrix (a 3x3 matrix in case of your example).
If the external EXCEL sheet is static and not subject to change you may also consider embedding it by creating an Excel component and then copy the data from the external sheet to it. PTC has provided no way to embed an already existing sheet - what a shame.
Another workaround using a template file was suggested here Insert existing excel component in mathcad sheet
Once the data is in the embedded sheet you can extract any data you like to Prime vectors or matrices.