So you just put it in the grocery cart while at the store.
Here are the dimensions

Which I took from Wayfair, where it is also available. I've had mine for 18 years. It holds up to 120 lbs and although I no longer use it for groceries, it does come in handy around the house from time to time.
When I used it for groceries, mine were packed in plastic bags from the store Heavy stuff on the bottom, lighter on top, and more could be hung from the handles. It holds a lot of groceries.
Here's a photo I took of it loaded during the early days of COVID 2020 when I would only go to the store about every two weeks.

Oddly enough, I bought the cart to ship with furnishings going to a house in Panama, which was on an island in the Bocas area. Shopping would be done on another island, so we'd have to bring groceries from there by boat to our house. It was intended as an escape from Bush. When Obama was elected, we figured we'd no longer need to leave the country, and sold the place in Panama after our house here burned down. Everything I had in storage to be shipped to Panama, I used to furnish a new place here. Somebody once told me I was lucky to have a house in a box and didn't have to start from scratch after the fire, which destroyed everything. Who knew I'd be using a collapsible cart years later during a pandemic, living in a high rise apartment? Life is so damn unpredictable.