Looking for a formula to calculate the total of several items automatically

Is there a formula? Yes, but there is not enough information in your post to create one.

To have a formula that calculates the number of sold items, you have to have the raw data for your sales. The only thing you have told is about is a list of items. Do you have your own separate sheets in Google Sheets? What does "fill out the table" mean? What table, what data is in the table, how do you fill it out? We need a lot more information, and may need a sample file depending on how complicated this gets.

For your second question please open a separate thread in The Water Cooler rather than piggybacking an off-topic question here.

You can just add a column for the monthly sales of each item, something like =SUM(B2:B30) to get the total for the month, having B2:B30 be your range of cells. If you would like to sum up any one item's total, you can use the SUMIF function. For example, if you want to find the total of "Item Name," then =SUMIF(A2:A30, "Item Name", B2:B30).
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