Your specific combination of ports isn’t necessarily easy to procure - but of options that are available you might consider a Kingston Nucleum USB-C hub - to which you would need to add an Apple USB-C to 3.5mm Headphone Adapter. Both can be used individually, or together, without removing your iPad’s case; both have a USB-C pigtail connector to connect to the iPad.
With many USB-C hubs, such as the Kingston, you can (and should) connect your USB-C Power Adapter to the hub’s USB-PD (Power Delivery) pass-though port. If you intend to simultaneously use the 3.5mm Headphone adapter, this is connected to the Kingston hub’s downstream USB-C port. In addition to a USB-PD, downstream USB-C and HDMI ports, the Kingston hub also features two USB3.1 Type-A ports plus SD and microSD card reader slots.
Kingston Nucleum
https://www.kingston.com/unitedkingdom/en/memory-card-readers/nucleum-usb-type-c-hub
USB-C to 3.5mm Headphone Jack Adapter
https://store.apple.com/uk/xc/product/MU7E2ZM/A
Be aware that most USB-C to HDMI Adapters/Hubs do not support HDCP - which may be an issue if you intend to mirror your iPad display to an external monitor or TV.
Apple do market their own USB-C Digital AV Multiport Adapter (which does support HDMI/HDCP) - but lacks a 3.5mm Headphone jack.
https://store.apple.com/uk/xc/product/MUF82ZM/A