There are two scenarios when you are importing inventory adjustment
1. The product you want to import is zero at the location
2. The product exists or has quantity at the location
In the first case the there is no record of that product so the field you would need to import are
- Counted Quantity
- Location or Location/external id
- Product or Product/external id
Second case would be
In the first case, which i believe is also your case, I prefer you use the external id of the products. If you choose to use the name however, it must match the exact same way odoo displays names of product.product (product variants) i.e "[internal ref] name (variant)". Using the exernal id is just better, easier and safer honestly
In the second case you need the id of the record in the "inventory adjustment module" to just update the counted quantity so make sure your csv file does not have products in a location that already exist in the model.
Let me know if it dosent work.