IIS URL Rewrite rules to redirect domain suffix (path) to different ports on the same Virtual Machine

Question

• I've made an A-record dev.ourcompany.com, pointing to the server IP-address
• Installed ARR Routing and enabled Proxy
• Installed URL Rewrite and made the following Rules: (screenshot with IIS config)

<rewrite>
    <rules>
        <rule name="thin" stopProcessing="true">
            <match url="thin" />
            <action type="Rewrite" url="http://10.10.10.21:6580/{R:0}" appendQueryString="true" />
        </rule>
        <rule name="grafana" stopProcessing="true">
            <match url="grafana" />
            <action type="Rewrite" url="http://10.10.10.21:3000/{R:0}" appendQueryString="true" />
        </rule>
    </rules>
</rewrite>

My goal is to have:

• dev.ourcompany.com/thin goto http://10.10.10.21:6580 (on the same server)
• dev.ourcompany.com/grafana goto http://10.10.10.21:3000 (on the same server)

I've tried:

• IIS rewrite rule to a different port
• Using query string to redirect/rewrite to different internal IIS sites
• https://stackoverflow.com/questions/36470848/iis-url-rewrite-domain-to-one-of-several-vms
• https://halfblood.pro/the-very-common-mistakes-when-using-iis-url-rewrite-module-a2ab7e4fee59

with no luck however. I get something like:

• 404: Not Found (and some other messages when playing around with the pattern ⬅️ I'm aware that the above pattern is probably wrong, but I've tried a lot of them...)

I've tried Server Farms, etc... but these things are not my strong point.

Tnx!