Can I charge my ipad pro 5th generation with an external battery pack or something like it?

Yes, you can charge an iPad using a suitable PowerBank - although it will need to have an adequate power output...

Most models of iPad require a Power source rated at 12W (i.e., 2.4A @5V) or greater to reliably charge. 5W Power Adapters/PowerBanks (1.0A @5V) intended for older models of iPhone are inadequate to charge an iPad; if the iPad charges at all, charging will be very slow. Recent models of iPad are supplied with a 20W USB-C Power Adapter.

Some third-party USB-C power adapters (and portable PowerBanks) may not support USB PD (Power Delivery). Power Delivery mutually negotiates the charging voltage; the source, load and cable are all elements involved in the negotiation protocol. Unless the Power Adapter explicitly supports USB PD, it will almost certainly fail to charge the iPad; proprietary charging standards, such as QC (Quick Charge), are not supported.

Many computer USB ports also cannot source sufficient power to charge an iPad. Unless explicitly designed for charging connected devices, computer USB ports are typically limited to 0.5-1A @5V (i.e., 2.5-5.0W).

A PowerBank that has USB Type-A connections, such as the item that you illustrate, will be limited to a maximum charging rate of 12W. As such, it may be adequate.

You might better consider a PowerBank that explicitly supports USB PD (Power Delivery) that will have USB-C connections. This will be able to charge your iPad Pro at its maximum supported ~20W charging rate - and itself will charge faster.

Also consider that your fifth generation iPad Pro itself has a large battery. While a PowerBank with a 20,000mAh battery will fully charge the iPad battery at least once, but a higher capacity PowerBank (e.g., 26,000mAh) may be more useful to you.

You're very welcome.