@JuliosJamby First, you'll need an ID column that goes from 1 to 6000 in your Excel Table.
Then do this,
ClearCollect(col1,Filter(yourExcelTable, ID>1 && ID<2001);
ClearCollect(col2,Filter(yourExcelTable, ID>2000 && ID<4001);
ClearCollect(col3,Filter(yourExcelTable, ID>4000 && ID<6001);
ClearCollect(colCombined, col1,col2,col3)