how setup own mdm server which will manage ios devices

Please understand that your query is thin on details. This makes any specific answer difficult to impossible to provide. Let me start by saying the following:

• Sign up for Apple Business Manager (this is not to be confused with Apple Business Essentials which is Apple's MDM). I am assuming you are a business. If you are not, you can still use an MDM but you will not be able to achieve automated enrollment (DEP) or volume app purchasing (VPP) as ABM is needed for those functions. DEP and VPP are the ultimate goals as they will streamline deployment and eliminate the need for Apple IDs to install App Store apps.

• If you have existing devices that were not, or cannot be, associated to ABM, you may need to erase them in order to side load them into ABM. This is disruptive. You might find it makes more sense to manually enroll the existing devices and accept the limitation on unsupervised assets until attrition can replace the units. Or, purchase a few new units AFTER ABM is setup and properly linked to your reseller. The new units will go through automated enrollment, achieving full supervision status. Give the units out and reset the old ones, sideloading as you go. This is the trickle down deployment method. You will eventually replace all units and achieve full supervision.

• Don't try to build your own MDM as there are no good options (Apple's Profile Manager has been discontinued and using Apple Configurator is for very narrow use cases in which devices remain stationary). Select a cloud MDM provider. There are many to choose from, including Jamf, Mosyle, Microsoft, Addigy, Hexnode, Apple, and many, many more. Do some research to determine features, prices, and approachability. For pure iOS management, the feature set is relatively consistent across products. However, if you have plans to also manage Macs, some MDMs are just better than others. To discover the limitations, you need to understand what you want from your MDM.

• Understand that deploying an MDM makes fleet management easy. But deploying MDM to manage a fleet is hard. If you have no prior experience, consider finding an expert to help you get setup. Deploying an MDM is like building a skyscraper. If you have a poor foundation, the entire structure can collapse on you. Be smart. Start smart. If you don't you will be living with your mistakes.

If you have a fleet of devices, MDM is the logical management solution. However, getting from where you are now to an effective MDM requires a lot of work and platform understanding.

Hope this is helpful,

Reid