Price per unit is a Shopify admin feature that is currently only available for merchants located in France or Germany - you can read more about this feature in Shopify's documents here.
Currently, our Flow themes have 'Price per unit' support installed as standard to allow the 'Price per unit' measurement to be displayed on the following pages:
Cart page & drawer
Collection list page
You can see an example of the functionality here:
To enable this function on your Shopify Product on Flow, please ensure that the following factors are all correct for your storefront:
Store location in France or Germany.
'Show unit price for this product' is enabled for the product .
A price and measurement has been assigned.
The product has no variants enabled.