You can use the Developer mode (https://www.odoo.com/documentation/18.0/applications/general/developer_mode.html) to find fields, models (and more) by simply hovering a field in any view.
In your case you seem to be referring to the field inventory_date in the model stock.quant - thus the table stock_quant:
Thank you. Didn't even think to look there. Love the developer mode!