Mediation is a voluntary process. That means that both you AND your ex-husband must agree to mediate.
In many states, you can have your attorney request a referral to mediation. This means that the court will order both of you to attend mediation. But attending doesn't necessarily mean your ex will mediate; it means he must at least show up to the mediation.
If you do get the court to refer you to mediation, many family courts have a mediation unit; others have a roster of available mediators, and you and your ex (through your attorneys) choose one.
The other way for you and your ex to get to mediator, is for each of you to agree to go, and again you and your respective attorneys can choose the mediator. You don't have to wait for the court to do anything for you both to go to mediation.
Most states keep a roster of mediators, including by area (such as family, civil, county, etc.) You can search your state's court sites to see if they have links to any such state roster.
Hope that helps.