Redirection using CloudFlare workers

worker.js

const base = "https://example.com";
const statusCode = 301;

async function handleRequest(request) {
    const url = new URL(request.url);
    let { pathname } = url;

    // Split the pathname into parts using '/'
    var parts = pathname.split('/');
    var firstPart = parts[1];
    var secondPart = parts[2];
    
    // you can modify this condition as per your need.  
    if( 'plugins' === firstPart || 'themes' === firstPart ) {
        const destinationURL = base + "?" + firstPart + "=" + secondPart;
        return Response.redirect(destinationURL, statusCode)
    }

    return fetch(request)
}

addEventListener("fetch", async event => {
    event.respondWith(handleRequest(event.request))
})