Adding list of values to another list of values (Inventory restocking)

Hi, I have been searching on this forum (and several other websites) for a solution to this problem. I'm sure it's relatively simple, but I guess I'm not familiar enough with Excel terminology to search properly for what exactly I need done.

I need to use Excel to restock my inventory. I need to be able to have a list of items in a recently received shipment, then add the values from that list to the corresponding entry in the master inventory file.

For example, let's say I have a master inventory list of 3,000 stock items. I order a shipment that restocks 1,000 of those 3,000 items based on the SKU number. Now I have two separate spreadsheets (one master inventory file, and one with the items to be restocked). What formula can I use to make Excel see the SKU number on the restock sheet, take the restock value from it, then look up the corresponding SKU number on the master inventory sheet, and add that value to the current value?

Please let me know if I have been unclear. As I said before I'm not great with Excel terminology!

Thank you in advance!

You can use sumif probably..

If the master list is in say A1:B3000 (item # in A, qty in B)
And the new shipment list is in say E1:F1000 (item # in E, qty in F)

in C1 and filled down put
=SUMIF(E$1:E$1000,A1,F$1:F$1000)

Then you can copy column C (with the formulas)
And right click column B - Paste Special - Values - Add