Replace Grav logo

I installed the Grav base package and its running on a web server. I added the first pages.
I use the installed standard Antimatter theme. I would like to replace the GRAV logo (it looks like a vector graphic without the astronaut). Into which folder do I have to upload the image file of my logo? Which file in which folder do I have to edit to tell Grav where it can find the logo file?

Just change the reference in the partials/base.html.twig file of the theme.

I found the file partials/base.html.twig and I assume I have to change the following code:

<div id="logo">
<h3><a href="{{ base_url == '' ? '/' : base_url }}">{{ config.site.title }}</a></h3>
</div>

Would you please tell me how the code has to look like, if I put the file "logo.jpg" into the folder user/themes/antimatter/images/ ?
I am sorry for this question, but I am not very experienced in this topic.

Dear Rhukster,
thank you so much for your excellent support!!!!
Replacing
<h3><a href=“{{ baseurl == '' ? ‘/’ : baseurl }}”>{{ config.site.title }}</a></h3>
in the file .../user/themes/antimatter/templates/partials/base.html.twig
with your code helped.