There’s already an invoice with 1030. You can use it again, but it resets your invoice numbers (starting from 1030).Do you still want to use this invoice number? Yes/No

I can share some information about creating an invoice in QuickBooks Online (QBO), @fatmaruzanna.

When you turn on the Custom transaction numbers feature, you can set your own numbering preference. If you choose Yes on that prompt, QuickBooks adds +1 to the number to get the next invoice number. On your next one, it'll be 1031. 

You can refer to this article for more information about setting up a numbering preference for your sales form: How to change the invoice number on sales forms.

Here's also detailed guidance on how to customise the appearance of your sales forms like your invoices, Customise invoices, estimates,and sales receipts in QuickBooks Online.

Let me know if I can be of further assistance with your invoices and or anything else, let me know by leaving a reply below. Take care and have a great rest of the day!