remove WooCommerce cart icon from nav bar

Just to clarify, do you mean this free theme: Oprum?

The last update was in early 2016, so you might want to look for a more up-to-date theme to make sure that the recent changes in WooCommerce work as you’d expect.

That said, you might be able to contact the theme’s author here: https://dinevthemes.com/support/ or find solutions in their documentation.

.header-cart {
  display: none;
}

As @valedeoro suggested, I have migrate to a more supported theme.
Thank you.

I’m glad to hear you found a good solution – thanks for letting us know!