Help Making Use Case Diagram

Basically I'm a noob with database work and just need a kick start to complete the rest of my other diagrams, seeing as the use case was the first step I thought I would ask for some help :D

So this is my situation, can someone help me make a use case diagram for someone buying a book from me;

""I own a business which sells textbooks and other
educational books to students attending local secondary schools and tertiary institutions.

I currently sell these items using a small shop in town but have decided to move to an online presence only to reduce the cost to students.

Currently, my business has an established database for inventory items and a sales system to record the details for sales made. Both of these systems will continue to be used and I may make reasonable assumptions as to the type of data these systems contain.

The sales
system captures details of sales made and updates the inventory system for items sold. The inventory system contains data about individual stock items held including purchase and
sale prices, item description, and quantity on hand. There is currently no system to show details about who buys items because all sales are based on cash (cash, cheque, credit
card, eftpos) transactions.""

Could a admin or forum mods please delete my original post and replace with the following;

Hey,

Basically im doing an assignment and have to help a local book store convert to a online book store. I need to make diagrams for the following: Use case, Function Decomposition, Conceptual erd, context, level 0 and level 1 and initial data dictionary.

I emailed various online stores all but denying me help.

Oh and before anyone posts saying just google it, yes i am well aware of how to use the internet and have searched, so please dont post that lol.

Now I know my chances of anyone willing to help me do this all or any, are pretty slim. So if anyone can help with the lot, please pm me and I can give you the full details on the assignment, please note there maybe an incentive.

So please help me out. Thanx GB.

Can a MOD delete this thread. Thanks