Do you mean Magento 1.3.
Are you seriously using Magento 1.3 till now? I am wondering.
Why don't you get your store on Magento 2.3.3?
It is very difficult you can find 1.3 compatible theme now.
They have written compatibility 1.3
Even themeforest has starting from Magento 1.4
Honestly, it will be a test and trial for you.