Change the name of invoice

Hi to everyone
i installed yesterday the invoiceplane. One problem i have is that i need to have different type of invoices.
In my country (Greece) we use an invoice with customer vat number for business and for regular non business customers a receipt without including customer vat number .
So each of them must have different number sequences .
As invoiceplane doesnt support that i decide to install it two times in my server in different folders (one installation to handle invoices for business customers and one folder to handle invoices-receipts for simple customers (worked fine with different databases, a minor problem is that i can be logged-in to one each time but that is not problem for what i want)

My problem is that in my second installation that i want to use it for simple receipts (without customers vat numbers) i want to change the name “invoice” to “receipt” (in Greek translation)
i guess i have to replace that name with the one i want, in one file/files in the server

where can i find them inside my installation in order to change it in the code ?

i dont care to have it changed to all menus… just only when i make the pdf file of the invoice/receipt

thanks in advance

ok i find the location of the translated files and changed them (worked)

in linux server with Apache server the destination is (with console commands) :

cd /var/www/html/your_invoicepalne_folder_name/application/language/
ls (to list language folders)
cd Greek (for my case )
nano ip_lang.php (and change the translated name in Greek for invoice to what i wanted to be )