By default, whenever you open the Excel, the horizontal scroll bar appears at the bottom which allows you to view more contents hide on the right.
If it disappears and you want it back, please follow the steps below:
Step 1: Click the "File" Tab from the ribbon;
Step 2: Click "Options" from the left navigation menu;
Step 3: Click "Advanced" from the left navigation menu in the dialog box;
Step 4: Check "Show horizontal scroll bar" under the section of "Display options for this workbook";
Step 5: Click "OK" at the bottom to apply the changes.