Hi Mate,
Big firm like H&R Block may have expertise on how to help you todo this . I am not an accountant, however based on my non accounting simple understanding is as long as you can work out the difference between what you sell and what you buy then you have your figure of profit or loss at the end of FY. Expenses related maybe deductible, just check with the accountant. Off course you need to convert the profit, loss and expenses related in USD to AUD. ATO publishes the rate for 30th June every financial year, you can google. Good luck.