Hi, The form you're looking for is: FLORIDA SUPREME COURT APPROVED FAMILY LAW FORM 12.903(e), ANSWER TO SUPPLEMENTAL PETITION. It is available for free download on the Florida Supreme Court's website - www.flcourts.org.
The instructions for that form state in part:
"This form should be used when you are responding to a supplemental petition for modification of Parenting Plan, time-sharing schedule, child support, or alimony. This form is used to admit or deny all of the allegations in the supplemental petition if you do not plan to file a counterpetition. There is no form for a counterpetition to a supplemental petition in these Family Law Forms. If you want to file a counterpetition to a supplemental petition you will need to either seek legal assistance or create a form yourself."