It’s common for the court to order one or both spouses to provide life insurance in a certain amount, with a trust for your kids as beneficiary or with your children directly as beneficiaries. This is intended to help support the children since your spouse can no longer do so. It’s also common for a spouse to be required to buy life insurance naming the ex-spouse as beneficiary as part of the alimony or spousal support part of the case.
If your divorce decree does not require that your ex carry a life insurance policy, in order to require him to get one, you would need to go back to court, ask for a modification, and show why the situation has changed that makes this necessary now. If the decree does require him to carry life insurance, you can ask for proof that the policy is in effect. If it is not in effect, you can file papers with the court and ask that the court enforce the decree.
If life insurance is not ordered as part of the divorce, he is free to do whatever he wants with his existing policies, including cancelling them, changing them so that you are not the beneficiary, or borrowing against the policies. In order to stop him from changing the policies, you would need to have those issues addressed in court.