Excel Formula / pivot table/ custom calculation

Description of excel work: the attached list contains a list of a large range of shoes - each time the product code ( sku ) contains _Parent -
and highlighted in yellow - this marks where a new shoe style starts and ends.

i need the spreadsheet to retain the same order but to show the total number of sales which is for each style

e.g. adam will have 16 sales
alan also has 16 sales
angus has 4 sales

--- the spreadsheet is approximately 10, 000 rows deep and has about 405 parents

this will take too long to manually calculated and add up one by one - therefore it will be good if somehow excel can separate the rows which contain parent - then create a pivot table to show a total of sales for each type -

someone who has experience of this should be able to do this job quickly
Extra notes: