Replace a json object array value dynamically in AzureDevops pipeline

A json file in my repository has object arrays. In Azure pipeline I want to read the file and replace certain object values before proceeding with other tasks like publishing, etc. Example json file :

    "Routes": [
        {
            "UpstreamPathTemplate": "/product",
            "DownstreamHostAndPorts": [
                {
                    "Host": "localhost",
                    "Port": 7133
                }
            ]
        },
        {
            "UpstreamPathTemplate": "/product/delete",
            "DownstreamHostAndPorts": [
                {
                    "Host": "localhost",
                    "Port": 7133
                }
            ]
        },
        {
            "UpstreamPathTemplate": "/order",
            "DownstreamHostAndPorts": [
                {
                    "Host": "localhost",
                    "Port": 7203
                }
            ]
        }
    ]

Now I want to pick the first unique word after '/' from UpstreamPathTemplate for each object and replace DownstreamHostAndPorts[0].Host with that word. Also all Port value should be 80. So after replacement above Json would look like

"Routes": [
        {
            "UpstreamPathTemplate": "/product",
            "DownstreamHostAndPorts": [
                {
                    "Host": "product",
                    "Port": 80
                }
            ]
        },
        {
            "UpstreamPathTemplate": "/product/delete",
            "DownstreamHostAndPorts": [
                {
                    "Host": "product",
                    "Port": 80
                }
            ]
        },
        {
            "UpstreamPathTemplate": "/order",
            "DownstreamHostAndPorts": [
                {
                    "Host": "order",
                    "Port": 80
                }
            ]
        }
    ]