pos[pos.length] =
   ss.getSheets()[sheetNumber + 13].getRange(teamRow + i, teamCol + 1).getValue();

var allSheets = ss.getSheets();
var targetSheetIndex = sheetNumber + 13;
var targetSheet = allSheets[targetSheetIndex];
var targetRow = teamRow + i;
var targetCol = teamCol + 1;
var targetCell = targetSheet.getRange(targetRow, targetCol);
var targetValue = targetCell.getValue();