Hi Fariha,
You can save data of form 1 to localStorage property at formSubmit event.
Because each input field has a specifc id attribute, hence we can get its value with document.getElementById("123").value method.

Script 1:
MsCrmMkt.MsCrmFormLoader.on('formSubmit', function (event) {
var firstName = document.getElementById("3f746946-34b4-442c-a677-e232cdd2bc40").value;
var lastName = document.getElementById("xxxx").value;
var emailAddress = document.getElementById("yyyy").value;
localStorage.setItem("firstname", firstName);
localStorage.setItem("lastname", lastName);
localStorage.setItem("emailaddress", emailAddress);
});
Then on the second landing page, get items from localStorage to fill fields of form 2.
Script 2:
MsCrmMkt.MsCrmFormLoader.on('afterFormRender', function (event) {
var firstName = document.getElementById("c98e6449-2f57-4058-aeee-546b0af11b5a");
var lastName = document.getElementById("aaa");
var emailAddress = document.getElementById("bbb");
firstName.value = localStorage.getItem("firstname");
lastName.value = localStorage.getItem("lastname");
emailAddress.value = localStorage.getItem("emailaddress");
});
Please refer to following articles for how to use marketing form API and localStorage property:
https://docs.microsoft.com/en-us/dynamics365/marketing/developer/marketing-form-client-side-extensibility
https://developer.mozilla.org/en-US/docs/Web/API/Window/localStorage
Regards,
Clofly