Hello @Adrian Mostoghiu ,
Thank you for reaching out to Microsoft Q&A platform. Happy to answer your question.
one method of creating a VM with an existing disk from on-premises VM is lift and shift method, which is what @Dave Patrick suggested as per prepare-for-upload-vhd-image
Another most reliable approach is Azure Site Recovery(ASR) migration of on-premises VM to azure. Also called as ASR H2A approach. It doesn't require you to do any manually steps. You need to install ASR agent on Hyper-V host and configure replication, and that would replicate your VM to azure. All that you need to validate is that the VM's OS is supported on Azure. Refer support matrix link here hyper-v-azure-support-matrix
For complete tutorial of replicating VM from Hyper-V to Azure, follow the link here : hyper-v-azure-tutorial
Please "Accept as Answer" and Upvote if any of above helped so that, it can help others in community looking for remediation for the similar issues.