You've done a lot of steps incorrectly. High Level--> you have an unbound form which means all the data you type into it goes nowhere. You should use bound forms, that way the data automatically goes into the tables they are based on. However...
You haven't set up your tables correctly. You have 1 table for a system that requires at least 2. You need a table for invoices (Invoice Number, Date, To, Address) and a table for Items (S. No, Particulars, Quantity, Rate).
Databases aren't spreadsheets they require a different way of thinking. I suggest you read up on normalization (
https://en.wikipedia.org/wiki/Database_normalization). That's the process of setting up tables correctly. Once you have done that,f I suggest you manually put in data into those tables, then you create your reports and then you focus on forms.
So, read up on normalization, give it a shot on your data, then post back any issues you have with just that. Let's hold off on forms for now.