how can I use the same keyboard and mouse with macbook and iPad

Your keyboard/mouse can only be paired to one device at a time. There is a device called a KVM switch but I am not familiar with it; however that may work but I believe there needs to be a cable connection and that would not work with an iPad - only with computers as far as I know.

https://www.raritan.com/blog/detail/understanding-the-four-categories-of-kvm-switches

IF your MacBook and iPad supports universal control, please see this instructions to set that up

To use Universal Control, make sure of the following:

• You’re using supported models of Mac and iPad.
• Your Mac has macOS 12.3 or later and your iPad has iPadOS 15.4 or later.
• You’re signed in with the same Apple ID with two-factor authentication on all your devices.
• You have Wi-Fi, Bluetooth and Handoff turned on in System Settings (on your Mac) and in Settings (on your iPad).

Connect your Mac to another Mac or iPad to use Universal Control

With Universal Control, you can establish a connection between your Mac and a nearby device, and then use a single keyboard and mouse or trackpad to work across the devices.

Note: If you don’t use Universal Control for a period of time, you may need to establish the connection again.

Do one of the following:

• On your Mac, use your mouse or trackpad to move the pointer to the right or left edge of the Mac screen. When a border appears at the edge of the Mac screen, move the pointer past the border until the pointer appears on the other device. 
• On your Mac, choose Apple menu  > System Settings, then click Displays  in the sidebar. (You may need to scroll down.) Click the  pop-up menu on the right, then choose a device below Link Keyboard and Mouse. Use your mouse or trackpad to move the pointer past the edge of the Mac screen until it appears on the other device. 
• On your Mac, click Control Centre in the menu bar, click Display, then choose a device below Link keyboard and mouse to. Use your mouse or trackpad to move the pointer past the edge of the Mac screen until it appears on the other device.

The direction in which you move the pointer when establishing the connection determines which side of the display you use to connect your devices. You can adjust this behaviour by changing the arrangement of the devices in Displays settings. Click the image of the display, then drag it to the desired position.

You can set your Mac to automatically reconnect to any nearby Mac or iPad. Choose Apple menu  > System Settings, then click Displays  in the sidebar. (You may need to scroll down.) Click Advanced on the right, then select Automatically reconnect to any nearby Mac or iPad.