Is it permissible for me to return to my country to work in a conventional bank currently, which will convert to an Islamic bank within two years, in order to care for my elderly parents?

Working in usurious banks is forbidden, and its prohibition varies in severity. Allah will grant success to whoever repents from working in these banks. As for working in the Islamic branch of a usurious bank, there is no objection to it if it adheres to Islamic legal controls; otherwise, it is not permissible.