Where can I find a step-by-step plan to migrate from on-prem to the cloud version?
That depends on what you want to achieve: a hybrid setup (on-prem linked with cloud) or a cloud-only setup.
We had an Expert Q&A session that covers this, which you can find here: https://community.lansweeper.com/t5/product-discussions/expert-q-amp-a-lansweeper-on-prem-and-cloud/...