[Vuejs]-Problems with extracting params in nuxt 3

No need for onMounted hook or async function here. You need to call the useRoute composable.

<script setup>    
const route = useRoute();
console.log(route.params.applicant_id)
console.log(route.params.id)
</script>

The problem lies within the underscores (_) used in your pages route name.

If you rename your page to exam-[id]-[applicant_id].vue, the route params, when accessing /exam-cl96q0u040000v1ocg2ffryio-3 look like this:

{id: 'cl96q0u040000v1ocg2ffryio', applicant_id: '3'}