Mac users can find the File Sharing feature in System Preferences > Sharing section. You can enable this feature to turn your Mac into a file server, then connect other Macs, Windows computers and mobile phones to your Mac to transfer files between them. You can connect to Mac file share from Windows PC, connect to MAC SMB share from iPhone, Android, etc. If you are looking to access Mac file sharing from iPhone and iPad, you only need the stock Files app which can be used as SMB client app to access Mac SMB shares.
Enable File sharing on Mac
To enable File Sharing on your Mac, click the Apple menu from the top menu bar, select System Settings > General > Sharing and then click on the ON/OFF toggle for File Sharing to turn it on.
Optionally, click the Information icon next to the On/Off toggle to select folders to share and specify which user you like to share the files with.

Connect Mac file sharing from iPhone iPad
Connect your iPhone or iPad to the same Wi-Fi as your Mac. Then open the Files app, click Browse tab from the bottom, then click the Menu(three dots inside a circle) at the top right corner and choose Connect to Server from the drop-down menu.

On the Connect to Server screen, you can type in your Mac IP address, computer name or Hostname. You can scroll up to the first screenshot above(System Settings > General > Sharing), the Hostname can be found at the bottom of the Sharing screen.

There are various ways you can find the IP address of your Mac computer. You can find your Mac IP address from the System Preferences or Terminal app. You can also find your Mac’s IP address by clicking on the Wi-Fi icon while holding down the Option key on your keyboard. When you do this, you will see a drop-down menu that displays additional information about your Wi-Fi connection, including your IP address, as well as other network-related details. Simply look for the “IP address” entry in the menu, and you should see your IP address displayed next to it.
Then choose Registered User, input your Mac login username and its password to connect. Once connected, you can copy files between your Mac and iPhone using the Files app, or share files from other apps and save them to Files app > Mac SMB share.

Access Windows SMB shares
On Windows PC, you can also find the SMB file sharing feature. Then follow the same steps as described above to connect iPhone to Windows shared folders and share files.