An iPad that won't boot to a running state - or has an unresolved hardware fault - will always have a zero trade-in value. The cost of repair, if needed, will often outweigh any potential trade-in value.
While your iPad9 may be beyond its warranty period, repair services for the iPad9 are still available.
For practical purposes, in lieu of repairing and returning your own iPad, Apple usually exchange a qualifying iPad for a renewed/refurbished iPad of the same model and specification. The cost of the exchange is the same as would otherwise be charged for repair. Unless you have benefit of an active AppleCare plan, an out-of-warranty repair while expensive will be somewhat less than the cost of a replacement iPad.
As for out-of-warranty repair costs, Apple offers a fixed-price price repair. You can verify eligibility and cost for your region/country here:
iPad Repair & Service - Apple Support
If you have an active AppleCare+ plan, the cost of repair is reduced to a small excess/deductible fee.