@jisbanioly ;

Let me state this I do not have Square for Retail the paid version, but have the Free version.  In the Free version I am not able to see the cost of my items or my purchase price.  So when I download my items I only see my sale price. 

I believe on the Square for Retail Paid plan you can export your Items with the Current Unit Cost and the New Unit Cost.  

Export your Square Items and REMEBER the name of this Original File and its location.

Export these as a CSV or Excel file. 

Open the Spreadsheet from above.

Rename the Spreadsheet to (TEST import markup) this way you made NO changes to the original if something is not right that you can upload the original

Create a column near the Current Unit Cost or New Current Cost column you want to markup

Then Freeze the Top Header Row.

Then Sort your Spreadsheet by the Category Row.

This will get your Categories in order.

Then go to the Top Line of Markup Column that you Created of the Beer Category

Domestic Beer (Category for Example)

In that column make a simple formula ( =Current Unit Cost  * 1.4) Where Current Unit cost is the cell with this information F2 for example

Copy that formula down and paste for all the Domestic Beer category

Now your markup Column should have prices that are marked up 40%

Then for Category Domestic Beers Lite repeat with (=Current Unit Cost * 1.45) if you want the markup by 45%   

Repeat for all your Categories.

If you want no markup the Formula would be ( =Current Unit Cost * 1)

Then save the edited file as (TEST import markup)

Upload this file to Square and choose Markup column to be your Square Price.

If after the upload the prices are not what you thought ...

upload your file that you downloaded Before doing these changes (original File I said to remember name of from beginning)

This will be faster than doing 1 by 1 but I have not seen a Markup % column for Square for Retail paid version

Here is a Article for bulk Uploading and Changing Prices that I also got the downloaded Column Headers from:

item-library-and-unit-cost-management 

Any other Questions just ask