Unless you go piece by piece in your store, this is impossible to do on Bricklink. The sellers have been promised for years that there would be inventory tools added to run our stores and another year goes by with no tools. That is why Brickstore is the only way to mass update the prices in your store.
On the main screen select Bricklink Store Inventory. It will automatically start downloading your store inventory.
Now you will have a file with all your store inventory. You can save it for a backup in case something goes wrong on BL or you accidentally erase your store. It is always good to have a backup. As with adding pieces, you can select all your store and click on the $ with the BL Head and all your pieces will be updated to the new prices. Getting these updates into your store is easy unless you have a large store. Bricklink can’t handle large amounts of data being updated. It gives you a warning about adding more than 1000 lots if info so you will have to select your store in large blocks.
Select as many parts on screen you want to update on BL and go to the Export again but this time select the 3rd option Mass Update. We don’t want to Upload this to your store otherwise you can double this in your inventory and mess things up.
This screen is actually the bottom of the screen that was used to add new pieces. Click Verify and it will show all the updates and finish it off. Now if you have a large store you can go back and do another block. This is a much quicker way than choosing one piece at a time on Bricklink to update.
These are just 2 things that can be done with Brickstore. On the main screen you can see where you can import your wanted list, orders and shopping cart. It took awhile to figure out Brickstore so I hope this will get you off to a quick start.