euref-fin

TM35FIN (EPSG:3067) <-> EUREF-FIN Geodetic (EPSG:4258) <-> Web Mercator (EPSG:3857)
                                                       <-> ETRS89 / GK19FIN (EPSG:3873)
                                                       <-> ETRS89 / GK20FIN
                                                       <-> ETRS89 / GK21FIN
                                                       <-> ETRS89 / GK22FIN
                                                       <-> ETRS89 / GK23FIN
                                                       <-> ETRS89 / GK24FIN
                                                       <-> ETRS89 / GK25FIN
                                                       <-> ETRS89 / GK26FIN
                                                       <-> ETRS89 / GK27FIN
                                                       <-> ETRS89 / GK28FIN
                                                       <-> ETRS89 / GK29FIN
                                                       <-> ETRS89 / GK30FIN
                                                       <-> ETRS89 / GK31FIN (EPSG:3885)
                                                       <-> ETRS89 / UTM zone 34N (EPSG:3046)
                                                       <-> ETRS89 / UTM zone 35N (EPSG:3047)
                                                       <-> ETRS89 / UTM zone 36N (EPSG:3048)

axis order

Output is always in east,north / lon,lat / x,y order, you can swap it yourself if you want or need to.