Right-click on sheet tab, and select Move or Copy;
Check "Create a copy";
In case you want to insert the copy of sheet into another (opened) workbook, select the target workbook. By default the current workbook is target;
Select the position where you want the new sheet to be inserted (before certain other sheet, or at end (i.e. as last sheet in workbook);
Clikk OK button. A copy of sheet is created with some order number added to end of previous sheet name as by-default new sheet name. Rename the new sheet;
In case you don't want some old data remaining in new sheet, select the whole datarange, uncheck any cells you want to preserve (like column headers, columns with formulas, etc.), and use "Clear Cells" from right mouse-click on selected datarange - all previous data from active selection is removed, but all formatting remains.

In case you had Named Ranges defined in your source sheet, then there may be some problems with them - you have to check them, and probably to delete some of them the Excel added there