Where do you keep the product data now? Are the images available online?
One way to upload products is through a CSV file, however, you need to prepare the data in a format acceptable by Shopify.
You can find more about it here: https://help.shopify.com/en/manual/products/import-export/import-products
As for categories, you'd need to import them as tags, and then create collections based on product tags.
I have the data in Shopify template. The images are on Dropbox as well as on my local machine. All items in the file have category tags on them. However, creating around 150 categories manually isn't something I was looking forward to. Surely, there might be an easier way to import categories to Shopify?!
There is an app Collection Import/Export that looks like it could do the job of importing collections. If it doesn't work as expected, then I can help with automating the import of categories through a custom script.
We have a detailed guide on uploading products using CSV files on Shopify. A CSV file can make things easier with faster-importing speed CSV files, also less memory being consumed with many more benefits. Kindly take a look at our guide, hope it helps!