Traefik certificatesResolvers conf for user certificate

I was able to use Let's Encrypt certificate for non-prod domain. But now want to use Digi Cert SSL certificate in Traefik v2 for production.

As per this documents I need to have following configuration

# Dynamic configuration
      certFile = "path/to/cert.crt"
      keyFile  = "path/to/cert.key"

  stores = ["default"]

and path/to/cert.crt & path/to/cert.key provided by Kubernetes Secret.

What would be the configuration for [certificatesResolvers] ?

I would say you don't need certificate resolver for something else than autogenerated let's encrypt certificates.

I can just omit following tls in IngressRoute ?

   certResolver: default
     - main:

I am not using IngressRoute, but Ingress and I don't specify any certResolver

You do not omit tls you omit certResolver.