Hello I am relatively new to databases despite having studied then briefly as part of my A-Level course.
I have been given the task of creating a database that would suit the needs of a specific company who previously relied on a paper-based system.

The company uses index cards, when a customer make an order their details are checked with the previous index cards if they have not traded with the company before a new card is created. The same is true if a new item or product is added.

The last thing is an invoice is created when a purchase is complete which contains relevant information from the index card for the customer and the item along with the date item costs and the total cost and two are printed, one for the customer and one for the company.

Essentially I'm asking for some support on what I believe would be suitable.
The obvious tables would be:
Customer Table- Store customer details
Item Table- Store item details
Possible Tables?
Order table- Stores the items chosen for a specific order, the date of the order and the total for items
Invoice Table- Takes the relevant details from each of the other tables.

As I've stated I find myself to be a slight novice at this and any support on whether these tables are suitable would be greatly appreciated

You're definitely on the right track in defining the tables first. Anything that you would have more than one of (like a customer, or an item) should be it's own table. Also, ask yourself if it is important, and can you describe it? If it's important, then it is worth saving. If you can describe it, then those would be your attributes. For instance, a customer is definitely important, but can you describe a customer? The answer is yes. A customer has a first name, a last name, an address, city, state, zip code, phone number(s), and more.

All in all, I think you're headed in the right direction.