The Store ID of your GrubHub Account is required to be provided to Grubhub in order for the configuration of the integration to take place.
There are 3 different ways to find this:
1- You can find your Merchant ID by logging on to https://restaurant.grubhub.com/login.
Their Store ID will be located at the top of your Grubhub for restaurants account Dashboard.
2- You can also find it under your customer-facing store URL:
3 - You can request it by contacting GrubHub Restaurant Care at (877) 799 0790